1. Month Year
doc.: IEEE yy/xxxxr0
Access Delay Reduction for FILS: Network Discovery & Access congestion Improvements
Nov 2011
Authors:
Name
Affiliations
Address
Phone
Santosh Abraham
Qualcomm Inc
5775 Morehouse Dr., San Diego, CA
George Cherian
Simone Merlin
Jouni Malinen
Qualcomm, Inc
Hermiankatu 6-8 D
Tampere, Finland
Santosh Abraham, Qualcomm Inc.
John Doe, Some Company

2. Abstract Month Year doc.: IEEE 802.11-yy/xxxxr0
The submission proposes techniques to improve the access behaviour for fast initial link set up.
Santosh Abraham, Qualcomm Inc.
John Doe, Some Company

3. Conformance w/ TGai PAR & 5C
Month Year
doc.: IEEE yy/xxxxr0
Sept 2011
Conformance w/ TGai PAR & 5C
Conformance Question
Response
Does the proposal degrade the security offered by Robust Security Network Association (RSNA) already defined in ? No
Does the proposal change the MAC SAP interface?
Does the proposal require or introduce a change to the architecture?
Does the proposal introduce a change in the channel access mechanism?
Does the proposal introduce a change in the PHY?
Which of the following link set-up phases is addressed by the proposal?
(1) AP Discovery (2) Network Discovery (3) Link (re-)establishment / exchange of security related messages (4) Higher layer aspects, e.g. IP address assignment
1,2
Santosh Abraham, Qualcomm Inc.
John Doe, Some Company

4. Motivation FILS can be hindered by the following
Month Year
doc.: IEEE yy/xxxxr0
Motivation
FILS can be hindered by the following
Excessive air link traffic generated by active scan
A probe request generating several probe responses from different APs
Passive scan requires waiting for the next beacon
Scanning multiple channels before converging on the channel of the required AP
Methods to reduce the impact of the latency of the above are presented here
Santosh Abraham, Qualcomm Inc.
John Doe, Some Company

5. Reducing the Number of Probe Responses - I
Month Year
doc.: IEEE yy/xxxxr0
Reducing the Number of Probe Responses - I
When Wildcard SSID is used in the Probe Request, all APs that hear the probe request send a response
Increases network load especially when several STAs are trying to associate simultaneously
Pointed out by Katsuo Yunoki et. al in contribution 1414
Other methods may be used to restrict the set of APs that respond to a probe request, however such methods have limitations, e.g.,
Include SSID in probe request
STA will have to know the precise SSID at each location. A provider may use different SSIDs at each location
Include HESSID (11u)
The HESSID will vary from location to location to location since all locations of a service providers AP cannot be expected to belong to the same ESS
Santosh Abraham, Qualcomm Inc.
John Doe, Some Company

6. Reducing the Number of Probe Responses - II
Month Year
doc.: IEEE yy/xxxxr0
Reducing the Number of Probe Responses - II
Solution: STA sends probe requests that includes a Network Identifier
Prevents multiple probe responses that could occur when wild card SSID is used.
Network Identifier incorporated by service provider at the time of device purchase and would be recognizable by APs of the service provider
One option for the network identifier may be the roaming consortium organization identifier (11u)
To further reduce the number of probe responses, an STAs that sees a probe response with the Network Identifier it is looking for should not send a probe request
Such an STA can directly begin association procedures with the AP
Association Steps when using Network Identifier
STA sends probe request with Network Identifier
Only APs that match Network Identifier send out probe response
Probe response may be sent as a broadcast frame, and all STAs listen to the probe-response
Probe response includes Anonce (for authentication/key generation)
STA selects one of the APs to send authentication and association request
STAs that listened to the probe response and are interested in associating with that AP can proceed to step 3 directly
Santosh Abraham, Qualcomm Inc.
John Doe, Some Company

7. Reducing the Number of Probe Responses - III
Termination of pending Probe Responses
AP may terminate a queued probe response to an STA (say STA1) if it “sees” an association request from STA1. The association request may be destined for another AP
Association request sent by the STA informs APs that it no longer needs the probe response
Broadcast of Probe Responses
AP may send a broadcast probe response when it receives several probe requests from different STAs
Broadcast probe response should include information elements that correspond each of the multiple probe requests
Santosh Abraham, Qualcomm Inc.

8. Month Year
doc.: IEEE yy/xxxxr0
Enhanced Passive Scan
Passive scan allows STAs to obtain information about surrounding Access Points without sending probe requests
Passive scan introduces delays since the STA has to wait for beacons of each AP until it sees the needed SSID
Proposed Solution:
STA listens to probe responses that are sent other STAs and avoid sending probe requests if an STA sees a probe response from an AP it can associate with
Santosh Abraham, Qualcomm Inc.
John Doe, Some Company

9. Searching Multiple Channels
Month Year
doc.: IEEE yy/xxxxr0
Searching Multiple Channels
Considerable latency is incurred if an STA needs to send probe request on multiple channels to obtain the best AP for association
To avoid this latency every AP can include the following information in its probe response
Whether it is accepting new associations
STA can avoid sending association requests
The load level on the AP’s channel and other channels
STA can move to the least loaded channel immediately
BSSID of each of the APs on the other channels
Anonce value of each of the APs on the other channels
Information between APs may be shared in the backhaul
Santosh Abraham, Qualcomm Inc.
John Doe, Some Company

10. Month Year
doc.: IEEE yy/xxxxr0
Conclusion
Reducing messaging overhead is critical to reducing the latency for FILS
Proposed techniques for reducing the latency by
Reducing number of probe responses
Reducing time in passive scan
Rapid channel selection
Santosh Abraham, Qualcomm Inc.
John Doe, Some Company

11. Summary of Concepts Support adding a Network ID to a probe request.
APs may have one or more Network IDs
APs respond to a probe request with a Network ID only if the Network ID matches the AP’s Network ID
Support allowing an AP to send a broadcast probe response when it receives several probe requests from different STAs
Probe response includes information elements corresponding multiple probe requests
Support adding information in beacon and/or probe response about other APs including APs in other channels, information includes:
BSSID
Load level
Network ID
Santosh Abraham, Qualcomm Inc.